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    SubjectRe: [PATCH 2/2] PCI, ACPI, x86: update MMCFG information when hot-plugging PCI host bridges
    On 04/10/2012 11:47 PM, Yinghai Lu wrote:
    > On Tue, Apr 10, 2012 at 3:32 AM, Kenji Kaneshige
    > <> wrote:
    >> Additionally, I think there is a remaining issue even if we change
    >> this check like below.
    >> if (!!(pci_probe & PCI_PROBE_MASK & ~PCI_PROBE_MMCONF))
    >> return 0;
    >> I think this check has an assumption that system has at least one
    >> MCFG table entry and it has been initialized before
    >> acpi_pci_root_add() is called. I think this doesn't work on the
    >> system that doesn't have MCFG and all the pci root bridge have
    >> _CBA (that is, all host bridges are hot-pluggable and BIOS is
    >> implemented in the way PCI FW spec defines). As a result, MMCONFIG
    >> would never be enabled on such systems. Could you double check this?
    > You are right.
    > We can just remove that checking.
    > But wonder if current x86_64 system support that.
    > All peer root buses can be physically removed ?
    It's theoretically possible that BIOS doesn't provide MMCFG or _CBA
    for the legacy (non-removable bus 0) host bridge.

    > Thanks
    > Yinghai

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